CSI reporting on PUSCH for carrier aggregation

ABSTRACT

Carrier aggregation allows concurrent transmission on multiple component carriers (CC) to increase the data rate. A user equipment (UE) device in a cellular network provides periodic or aperiodic channel state information of the DL channel to a base station (eNB) for each of the aggregated CCs. The UE receives two or more reference signals corresponding to two or more aggregated CCs from an eNB. The UE computes a plurality of channel state information (CSI) reports for each of two or more aggregated CCs derived from the two or more reference signals. The UE receives a positive CSI request from the eNB for a CSI report and transmits CSI feedback to the eNB comprising one or more CSI reports selected from the plurality of CSI reports.

CLAIM TO PRIORITY UNDER 35 U.S.C. 119(e)

The present application claims priority to and incorporates by referenceU.S. provisional application No. 61/354,797 filed on Jun. 15, 2010,entitled “CSI Reporting in PUSCH for Carrier Aggregation.” The presentapplication also claims priority to and incorporates by reference U.S.provisional application No. 61/359,929 filed on Jun. 30, 2010, entitled“CSI Reporting in PUSCH for Carrier Aggregation.” The presentapplication also claims priority to and incorporates by reference U.S.provisional application No. 61/373,913 filed on Aug. 16, 2010, entitled“CSI Reporting in PUSCH for Carrier Aggregation.” The presentapplication also claims priority to and incorporates by reference U.S.provisional application No. 61/374,339 filed on Aug. 17, 2010, entitled“CSI Reporting in PUSCH for Carrier Aggregation.” The presentapplication also claims priority to and incorporates by reference U.S.provisional application No. 61/414,139 filed on Nov. 16, 2010, entitled“CSI Reporting in PUSCH for Carrier Aggregation.” The presentapplication also claims priority to and incorporates by reference U.S.provisional application No. 61/418,614 filed on Dec. 1, 2010, entitled“CSI Reporting in PUSCH for Carrier Aggregation.”

FIELD OF THE INVENTION

This invention generally relates to wireless cellular communication, andin particular to carrier aggregation in orthogonal and single carrierfrequency division multiple access (OFDMA) (SC-FDMA) systems.

BACKGROUND OF THE INVENTION

Wireless cellular communication networks incorporate a number of mobileUEs and a number of NodeBs. A NodeB is generally a fixed station, andmay also be called a base transceiver system (BTS), an access point(AP), a base station (BS), or some other equivalent terminology. Asimprovements of networks are made, the NodeB functionality evolves, so aNodeB is sometimes also referred to as an evolved NodeB (eNB). Ingeneral, NodeB hardware, when deployed, is fixed and stationary, whilethe UE hardware may be portable.

User equipment (UE), also commonly referred to as a terminal or a mobilestation, may be a fixed or mobile device and may be a wireless device, acellular phone, a personal digital assistant (PDA), a wireless modemcard, and so on. Uplink communication (UL) refers to a communicationfrom the UE to the NodeB, whereas downlink (DL) refers to communicationfrom the NodeB to the UE. Each NodeB contains radio frequencytransmitter(s) and the receiver(s) used to communicate directly with theUE, which may move freely around it. Similarly, each UE contains radiofrequency transmitter(s) and the receiver(s) used to communicatedirectly with the NodeB. In cellular networks, the UE cannot communicatedirectly with each other but have to communicate with the NodeB.

Long Term Evolution (LTE) wireless networks, also known as EvolvedUniversal Terrestrial Radio Access (E-UTRA), are being standardized bythe 3GPP working groups (WG). The Technical Standards Group Radio AccessNetwork (TSG RAN) group is responsible for the definition of thefunctions, requirements and interfaces of the UTRA/E-UTRA network in itstwo modes, FDD & TDD. OFDMA (orthogonal frequency division multipleaccess) and SC-FDMA (single carrier FDMA) access schemes were chosen forthe down-link (DL) and up-link (UL) of E-UTRA, respectively. Userequipments are time and frequency multiplexed on a physical uplinkshared channel (PUSCH), and a fine time and frequency synchronizationbetween UE's guarantees optimal intra-cell orthogonality. In case the UEis not UL synchronized, it uses a non-synchronized Physical RandomAccess Channel (PRACH), and the Base Station provides some allocated ULresource and timing advance information to allow the UE to transmit onthe PUSCH. The general operations of the physical channels are describedin the EUTRA specifications, for example: “3^(rd) Generation PartnershipProject; Technical Specification Group Radio Access Network; EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation (TS 36.211 Release 8, or later).”

Several types of physical channels are defined for the LTE downlink. Onecommon characteristic of physical channels is that they all conveyinformation from higher layers in the LTE stack. This is in contrast tophysical signals, which convey information that is used exclusivelywithin the physical (PHY) layer. Currently, the LTE DL physical channelsare as follows: Physical Downlink Shared Channel (PDSCH), PhysicalBroadcast Channel (PBCH), Physical Multicast Channel (PMCH), PhysicalControl Format Indicator Channel (PCFICH), Physical Downlink ControlChannel (PDCCH), and Physical Hybrid ARQ Indicator Channel (PHICH).

A reference signal (RS) is a pre-defined signal, pre-known to bothtransmitter and receiver. The RS can generally be thought of asdeterministic from the perspective of both transmitter and receiver. TheRS is typically transmitted in order for the receiver to estimate thesignal propagation medium. This process is also known as “channelestimation.” Thus, an RS can be transmitted to facilitate channelestimation. Upon deriving channel estimates, these estimates are usedfor demodulation of transmitted information. In downlink transmission,two types of reference signals are available. The first type ofreference signal is un-precoded and is transmitted over the entiresystem bandwidth of a cell, and is generally referred to ascell-specific reference signal (CRS). Another type of reference signalis modulated by the same precoder as applied on the data channel, andtherefore enables a UE to estimate the effective precoded MIMO (multipleinput multiple output) channel characteristics. This type of RS issometimes referred to as De-Modulation RS or DMRS. DMRS is transmittedonly when a UE is being scheduled, and is therefore only transmittedover the frequency resource assignment of data transmission. DMRS canalso be applied in uplink transmission (PUSCH), in case a UE transmitteris equipped with multiple antennas. An RS may also be transmitted forother purposes, such as channel sounding (SRS), synchronization, or anyother purpose. Also note that the Reference Signal (RS) can be sometimescalled the pilot signal, or the training signal, or any other equivalentterm.

The LTE PHY can optionally exploit multiple transceivers and antenna atboth the base station and UE in order to enhance link robustness andincrease data rates for the LTE downlink. Spatial diversity can be usedto provide diversity against fading. In particular, maximal ratiocombining (MRC) is used to enhance link reliability in challengingpropagating conditions when signal strength is low and multipathconditions are challenging. Transmit diversity can be used to improvesignal quality by transmitting the same data from multiple antennas tothe receiver. Spatial multiplexing can be used to increase systemcapacity by carrying multiple data streams simultaneously from multipleantennas on the same frequency. Spatial multiplexing may be performedwith one of the following, for example: cyclic delay diversity (CDD)precoding methods: zero-delay, small-delay, or large-delay CDD. Spatialmultiplexing may also be referred to as MIMO (multiple input multipleoutput).

With MRC, a signal is received via two (or more) separateantenna/transceiver pairs. The antennas are physically separated, andtherefore have distinct channel impulse responses. Channel compensationis applied to each received signal within the baseband processor beforebeing linearly combined to create a single composite received signal.When combined in this manner, the received signals add coherently withinthe baseband processor. However, the thermal noise from each transceiveris uncorrelated, resulting in improved signal to noise ratio (SNR). MRCenhances link reliability, but it does not increase the nominal maximumsystem data rate since data is transmitted by a single antenna and isprocessed at the receiver via two or more receivers.

MIMO, on the other hand, does increase system data rates. This isachieved by using multiple antennas on both the transmitting andreceiving ends. In order to successfully receive a MIMO transmission,the receiver must determine the channel impulse response from eachtransmitting antenna. In LTE, channel impulse responses are determinedby sequentially transmitting known reference signals from eachtransmitting antenna. While one transmitter antenna is sending thereference signal, the other antenna is idle on the same time/frequencyresources. Once the channel impulse responses are known, data can betransmitted from both antennas simultaneously. The linear combination ofthe two data streams at the two receiver antennas results in a set oftwo equations and two unknowns, which are resolvable into the twooriginal data streams.

Physical channels are mapped to specific transport channels. Transportchannels are service access points (SAPs) for higher layers. Eachphysical channel has defined algorithms for bit scrambling, modulation,layer mapping, precoding, and resource assignment. Layer mapping andprecoding are related to MIMO applications. Basically, a layercorresponds to a spatial multiplexing channel. Channel rank can varyfrom one up to the minimum of number of transmit and receive antennas.For example, given a 4×2 system, i.e., a system having four transmitantennas and two receive antennas, the maximum channel rank is two. Thechannel rank associated with a particular connection varies in time andfrequency as the fast fading alters the channel coefficients. Moreover,the channel rank determines how many layers, also referred to as thetransmission rank, can be successfully transmitted simultaneously. Forexample, if the channel rank is one at the instant of the transmissionof two layers, there is a strong likelihood that the two signalscorresponding to the two layers will interfere so much that both of thelayers are erroneously detected at the receiver. In conjunction withprecoding, adapting the transmission to the channel rank involvesstriving to use as many layers as the channel rank. Layer mappingspecifies exactly how the extra transmitter antennas are employed. Fornon-codebook based precoding, the precoding applied for the demodulationreference signal (DMRS) is the same as the one applied for the PUSCH(for uplink) and PDSCH (for downlink). Multiplexing of the demodulationreference signals can be time-division multiplexing, frequency divisionmultiplexing, code division multiplexing or a combination of them.

Precoding is used in conjunction with spatial multiplexing. The basicprinciple involved in precoding is to mix and distribute the modulationsymbols over the antennas while potentially also taking the currentchannel conditions into account. Precoding can be implemented by, forexample, multiplying the information carrying symbol vector containingmodulation symbols by a matrix which is selected to match the channelbased on a certain selection criterion. Some examples of selectioncriterion include average throughput and maximumsignal-to-interference-noise ratio (SINR). Sequences of symbol vectorsthus form a set of parallel symbol streams and each such symbol streamis referred to as a “layer”. Thus, depending on the choice of precoderin a particular implementation, a layer may directly correspond to acertain physical antenna or a layer may, via the precoder mapping, bedistributed onto several physical antennas.

In LTE Rel-8, single layer beamforming on antenna port 5 is alreadysupported. Single-layer beamforming is based on non-codebook precodingand relies on a dedicated demodulation reference symbol (DMRS) for datademodulation. DMRS symbols are precoded with the same precoding matricesas the PDSCH data symbols and therefore enable UE to estimate the“effective” channel after precoding. Rank-1 transmission is enforced. AUE is restricted to receive a single transport block (codeword) which ismapped to one layer (data stream) in DL transmission. From the UE'sperspective, the effective 1-layer channel appears as if data istransmitted from a single virtual antenna. DMRS corresponding to thislayer is defined as antenna port 5 in LTE Rel-8 to enable channelestimation.

A very simple multi-user MIMO (MU-MIMO) scheme is currently supported in3GPP LTE Rel-8 specification. A higher-layer configured semi-staticMU-MIMO mode is configured so that a UE knows that the eNB will attemptto schedule it with one or multiple other UEs. Codebook-based precodingis used where the precoding matrices for a UE are selected from apre-defined set (i.e. codebook) of fixed matrices (i.e. precodingmatrices/vectors). CQI feedback is important for informing the DLchannel status to the eNB in order to perform accurate DL linkadaptation (e.g. rank, precoding matrices, modulation and codingschemes, frequency-selective scheduling) and UE scheduling. Since a UEdoes not know which other UEs it will be scheduled together and whatprecoding matrices will be used for the co-schedule UE, CQI feedback inRel-8 is based on single-user MIMO (SU-MIMO) precoding.

3GPPs Organizational Partners have agreed to widen 3GPP′s scope toinclude the development of systems beyond 3G Release 8/9. One of the keyfeatures of Release 10 will be enhanced peak data rates to supportadvanced services and applications: 100 Mbit/s for high and 1 Gbit/s forlow mobility.

BRIEF DESCRIPTION OF THE DRAWINGS

Particular embodiments in accordance with the invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings:

FIG. 1 is a pictorial of an illustrative telecommunications network inwhich an embodiment of the invention is used to provide channel stateinformation (CSI) for multiple downlink component carriers for MIMOtransmission signals;

FIG. 2 is an illustrative format of one subcarrier (tone) of a DLtransmission subframe for use in the network of FIG. 1;

FIG. 3 illustrates aperiodic triggering of three cycles of CSI feedbackfrom two DL CCs;

FIGS. 4A-4C illustrate cases for CQI triggering by SIB2-linkage;

FIG. 5 illustrates triggering aperiodic CSI reports from a subset offive DL CCs using a bitmap;

FIG. 6 is a flow chart illustrating operation of CSI reporting used inthe network of FIG. 1; and

FIG. 7 is a block diagram illustrating an exemplary portion of acellular network with a base station in communication with a mobiledevice.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Carrier aggregation allows concurrent transmission on multiple componentcarriers (CC) to increase the data rate. The aggregated CCs can becontiguous or non-contiguous in the same radio frequency (RF) band, orthey may be located in different RF bands. UE feedback is important toreport downlink channel state information (CSI) to the eNB to enableclosed-loop MIMO beamforming and frequency-selective scheduling. ForRel-8/9 systems CSI feedback can be periodic on PUCCH and aperiodic onPUSCH. To maintain the single carrier property, periodic CSI istransmitted on the PUSCH when an UL grant coincides in the same subframewith a periodic CSI report. On the other hand, aperiodic CSI feedback onPUSCH is triggered by setting the (1-bit) CQI request field to “1” inthe UL grant. Furthermore, aperiodic CSI can be transmitted on the PUSCHwith or without UL-SCH data. In general, Rel-10 systems require higherCSI feedback accuracy, and larger CSI feedback payload to accommodateCSI reporting for multiple DL CCs. Therefore, aperiodic CSI transmissionis considered important in Rel-10 to fully reap the performance gainpromised by Rel-10 features including carrier aggregation and enhancedDL MIMO (8Tx SU-MIMO and MU-MIMO).

Several embodiments for improved CSI feedback on the PUSCH are describedin this disclosure. Feedback schemes to support periodic/aperiodic CSIfeedback for up to five DL component carriers on the physical uplinkshared channel (PUSCH) will be described herein.

For best operation, a transmitter must have knowledge of the channel,which is provided by the UE on the uplink control channel. This processis generally referred to as channel state information (CSI) feedback.This knowledge may include a channel quality index (CQI), a precodingmatrix Indicator (PMI), and a rank indication (RI). CSI feedback(RI/PMI/CQI) are recommended MIMO transmission properties derived at theUE based on the channel estimation. For example, RI is the recommendednumber of transmission layers (rank). PMI reflects the recommendedprecoding matrices within the recommended rank (RI). CQI is the observedchannel quality indicator (e.g. recommended modulate and coding scheme)assuming that the RI/PMI feedback are used for MIMO precoding. The PMIfeedback uses a codebook approach to provide an index into apredetermined set of precoding matrices. For 2×2 MIMO, there may bethree different codewords for rank-2 precoding, and four differentcodewords for rank-1 precoding; for 4×2 there may be 16 codewords forrank-1 and rank-2, respectively. Since the channel is continuallychanging, sub-band CQI and PMI information may be provided for multiplepoints across the channel bandwidth, at regular time intervals, up toseveral hundred times a second. The RI is typically provided at a muchlower rate on a wideband basis.

A downlink multiuser MIMO (DL MU-MIMO) communication system involves asingle eNB transmitting to multiple UEs at the same time over the samefrequency bandwidth. One example of DL MU-MIMO scheme is the dirty-papercoding approach, which from the information theory perspective is theoptimal MU-MIMO scheme in terms of achieving the maximum sum capacity.An alternative and more practical MU-MIMO scheme is transmit precoding,where the data to each UE is multiplied to a UE-specific precodingmatrix and then transmitted at the eNB antenna array simultaneously.

A UE that can best estimate channel conditions and then signal the bestcoding to use will get the best performance out of the channel. Althoughthe use of a codebook for precoding limits the best fit to the channel,it significantly simplifies the channel estimation process by the UE andthe amount of uplink signaling needed to convey the desired precoding.

The general procedure for determining and specifying CQI and PMI isdefined in the EUTRA specifications, for example: “3^(rd) GenerationPartnership Project; Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layerprocedures (TS 36.213 Release 8, or later),” which is incorporated byreference herein.

FIG. 1 is a pictorial of an illustrative telecommunications network 100in which an embodiment of the invention is used to support single userand multiuser MIMO transmission signals, as described in more detailbelow. The illustrative telecommunications network includes eNBs 101,102, and 103, though in operation, a telecommunications network mayinclude many more eNBs or fewer eNBs. Each of eNB 101, 102, and 103 isoperable over corresponding coverage areas 104, 105, and 106. Each eNB'scoverage area is further divided into cells. In the illustrated network,each eNB's coverage area is divided into three cells. Handset or otherUE 109 is shown in Cell A 108, which is within coverage area 104 of eNB101. Transmission is occurring between eNB 101 and UE 109 via downlinkchannel 110 and uplink channel 112. As UE 109 moves 116 out of Cell A108, and into Cell B 107, UE 109 may be “handed over” to eNB 102.

When UE 109 is not up-link synchronized with eNB 101, non-synchronizedUE 109 employs non-synchronous random access (NSRA) to requestallocation of up-link 112 time or frequency or code resources. If UE 109has data ready for transmission, for example, traffic data, measurementsreport, tracking area update, etc., UE 109 can transmit a random accesssignal on up-link 112 to eNB 101. The random access signal notifies eNB101 that UE 109 requires up-link resources to transmit the UE's data.ENB 101 responds by transmitting to UE 109, via down-link 110, a messagecontaining the parameters of the resources allocated for UE 109 up-linktransmission along with a possible timing error correction. Afterreceiving the resource allocation and a possible timing adjustmentmessage transmitted on down-link 110 by eNB 101, UE 109 may adjust itstransmit timing, to bring the UE 109 into synchronization with eNB 101,and transmit the data on up-link 112 employing the allotted resourcesduring the prescribed time interval. eNB 101 also sends a downlink grantto UE 109 when the eNB has data to transmit to UE 109. The downlinkgrant specifies one or more resource blocks on which the eNB willtransmit to the UE on downlink 110.

Similarly, UE 117 may communicate with eNB 101 on downlink 111 anduplink 113. eNB 101 may decide to send data on DL 111 in SU-MIMOtransmission to UE 117. Alternatively, eNB 101 may decide to send dataon DL 110 to UE 109 and on DL 111 to UE 117 in MU-MIMO transmissionusing the same frequency resources, as will be described in more detailbelow. In either case, an improved scheme for providing CSI reportsindicative of aggregated component carriers (CC) is embodied in each UEand used by the eNB for improved scheduling and downlink datatransmission, as will be described in more detail below.

Implicit Channel State Information (CSI) Feedback

With spatial multiplexing, a base station (Evolved Universal TerrestrialRadio Access Node B or eNB) may send multiple data streams (or layers)to UEs in downlink transmission using the same frequency. The number ofsuch layers or streams is defined as the rank. For LTE Rel-8, a UE needsto estimate the DL channel and report the recommended rank indicator(RI) to the serving eNB. The UE also must report the channel qualityindicator (CQI) and the precoding matrix indicator (PMI) which is anindex to the precoding matrix in a codebook. These indicators form a setof recommended transmission property to the serving eNB. Upon receivingthis feedback from the UE (RI/PMI/CQI), the eNB performs correspondingdownlink MIMO transmission scheduling.

Implicit CSI (CQI/PMI/RI) feedback are based on a pre-defined set ofcodebooks, which are a set of matrices calculated offline and known atthe eNB and UE. Codebook of rank-r consists of a number of Nt×r matriceswhere Nt is the number of eNB transmit antennas. UE feedback includesthe following information:

Rank indicator (RI): number of data stream;

Precoding matrix indictor (PMI): the index of the UE recommendedprecoding matrix in the rank-r codebook. For E-UTRA LTE Rel-8, a singlePMI is reported for each frequency subband, corresponding to the RIreport; and

Channel quality indicator (CQI): quality of the channel (e.g. in theform of supportable data rate, SNR). The reported CQI is associated withthe reported PMI.

FIG. 2 is an illustrative format of one subcarrier (tone) of a DLtransmission subframe for use in the network of FIG. 1. It includes 14resource elements. Elements of the present invention will be describedin the context of EUTRA sub-frame, even though its applicability isbroader. Orthogonal frequency division multiple access (OFDMA) basedsystems include classic OFDMA as well as its alternatives, like singlecarrier frequency division multiple access (SC-FDMA) and discreteFourier transform (DFT)-spread OFDMA. In OFDMA based systems, frequencyresources are divided into tones. Tones are further grouped into “toneblocks” or “resource blocks” for purposes of frequency-dependentscheduling of mobiles, and other possible purposes. Thus, each mobilecan be allocated one or more resource blocks in an OFDMA based system.This group of resource blocks will be denoted as the frequencyallocation for a given mobile.

FIG. 2 illustrates just one subcarrier of sub-frame 200 comprising twoslots 201 and 202. It includes 14 resource elements. Duration of theEUTRA sub-frame is 1 ms, which means that duration of two slots 201 and202 is 0.5 ms each. Each slot comprises seven OFDM symbols when a normalcyclic protection field (CP) is appended to each symbol, or six symbolswhen an extend CP is appended to each symbol. For example, slot 201comprises symbols 203-209. The slot 202 comprises symbols 210-216.Symbols 208, 209, 215 and 216 are Demodulation (DM) Reference symbols(RS), and are used to derive channel estimates which are needed forcoherent demodulation of the remaining symbols that are modulated withpayload data. LTE Rel 9 also defines several other antenna portconfigurations for antenna ports 0-3 and 5, where port 0-3 areunprecoded cell-specific reference symbols (CRS) antenna ports and port5 is DMRS for single-layer data transmission defined in Rel-8. Eachsymbol has a time duration equal to approximately T, which is a functionof the slot time. In this embodiment, the slot time is 500 μsec. Sincethe first symbol in the slot has more cyclic prefix samples, not allsymbols are exactly equal in duration, as per 3GPP TS36.211.Nevertheless, all symbols can be considered to be approximately equal induration, which doesn't exceed 75 μsec. Note that if all symbols wereexactly equal in duration, the symbol time T would approximately beequal to 500 μsec/7=71.4 μsec.

In some embodiments of the invention, the set of reference signalsequences comprises CAZAC sequences and near—CAZAC sequences. Near—CAZACis a term which designates sequences which are obtained using computersearch methods, and whose properties approximate CAZAC properties. Insome embodiments of the invention, CAZAC sequences are Zadoff—Chusequences. In some embodiments of the invention, near—CAZAC sequencesare sequences of the form exp(j*π*φ(n)/4); wherein the length of φ(n) isan integral multiple of 12. Here, “j” is the imaginary unit.

In some embodiments of the invention, the set of reference signalsequences comprises CAZAC sequences only. In some embodiments of theinvention, the set of reference signal sequences comprises near—CAZACsequences only. In some embodiments of the invention, the set ofreference signal sequences comprises both CAZAC sequences and near—CAZACsequences. Sometimes, a phase ramp is applied to modify the firstsequence, for example exp(j*n*α+j*π*φ(n)/4) can still be considered as areference signal sequence. For 3GPP EUTRA, there are 30 possiblesequences of length 24, which are also near—CAZAC. For length 36 andmore, sequences are produced from CAZAC sequences. Thus, the set ofreference signal sequences comprises both CAZAC and near—CAZACsequences.

Further details on the construction of reference signals, demodulationreference signals and sounding reference signals are included in 3rdGeneration Partnership Project; GPP TS 36.211 V9.1.0 (2010) “TechnicalSpecification Group Radio Access Network; Evolved Universal TerrestrialRadio Access (E-UTRA); Physical Channels and Modulation,” in particularin section 6 and which is incorporated herein by reference.

As mentioned earlier, carrier aggregation allows concurrent transmissionon multiple component carriers to increase the data rate. The aggregatedCCs can be contiguous or non-contiguous in the same RF band, or they maybe located in different RF bands. UE feedback is important to reportdownlink channel state information to the eNB to enable closed-loop MIMObeamforming and frequency-selective scheduling. For Rel-8/9 systems CSIfeedback can be periodic on PUCCH and aperiodic on PUSCH. To maintainthe single carrier property periodic CSI is transmitted on the PUSCHwhen an UL grant coincides in the same subframe with a periodic CSIreport. On the other hand aperiodic CSI feedback on PUSCH is triggeredby setting the (1-bit) CQI request field to “1” in the UL grant.Furthermore, aperiodic CSI can be transmitted on the PUSCH with orwithout UL-SCH data. In general, Rel-10 systems require higher CSIfeedback accuracy, and larger CSI feedback payload to accommodate CSIreporting for multiple DL CCs. Therefore, aperiodic CSI transmission isconsidered important in Rel-10 to fully reap the performance gainpromised by Rel-10 features including carrier aggregation and enhancedDL MIMO (8Tx SU-MIMO and MU-MIMO). Several design choices for CSIfeedback on the PUSCH will now be described.

Terminology

-   PCC: primary component carrier, it is always present for a UE. For    the purpose of data transmission and reception by a UE it is also    denoted as the primary serving cell (PCell).-   SCC: secondary component carrier, the UE can be configured for one    or more SCC. For the purpose of data transmission and reception by a    UE it is also denoted as a secondary serving cell (SCell).-   CSICC: the downlink CC whose CSI is reported-   N_(CC) ^(DL): the number of DL CCs (or DL serving cells) that are    configured for a specific UE.    Aperiodic CSI Feedback

It has been agreed that only one PUSCH carries UCI (uplink controlinformation) in the case of carrier aggregation. Therefore one UL grantmay trigger CSI feedback for several (N) DL CCs, with severalpossibilities:

Case 1: N=1: one UL grant triggers CSI feedback for one DL CC.

Case 2: N=N_(CC) ^(DL): one UL grant triggers CSI feedback for allN_(CC) ^(DL) CCs.

Case 3: N ε [1, N_(CC) ^(DL)] is configurable

In the following sub-sections the need and required signaling for eachcase will be discussed. Embodiments of the invention provide methods andconfigurations that define the following criteria: 1) how to indicatethe desired CSICCs; and 2) which UL CC conveys the aggregated CSIfeedback in a subframe with multiple UL grants.

Case 1: N=1

Similarly to Rel-8/9, the CQI request bit in the UL DCI (downlinkcontrol information) format is used to trigger CSI feedback for one DLCC. This scheme achieves the maximum commonality with Rel-8/9 in termsof CSI multiplexing on PUSCH. Hence if CSI coding and resourcedimensioning follows the same rules as in Rel-8, N=1 minimizes thespecification change of the PUSCH even with the proposed Rel-10 DL MIMOdouble codebook structure of W1 and W2.

For a single-antenna UE this is beneficial in terms of minimizing the UEimplementation impact. For a multi-antenna UE, maintaining the samePUSCH processing may be less critical because UCI multiplexing(especially RI) is different from Rel-8.

One disadvantage of Case I is the limited CSI feedback payload since anUL grant can only trigger one CC report. Therefore, CSI feedback reportsfor all N_(CC) ^(DL) CCs may need to be time-multiplexed. For example:CC scanning or multiple UL grants triggering multiple PUSCH. Other thanthe increased feedback delay and impaired CSI accuracy, the UL grantoverhead increase should be taken into account. For example, if one ULgrant triggers a one-shot CSI report for one DL CC, N_(CC) ^(DL) grantsare needed to trigger CSI for N_(CC) ^(DL) CCs. Alternatively, one ULgrant may trigger a block of periodic CSI reporting on PUSCH formultiple DL CCs, which comprises M cycles of PUSCH report where eachcycle includes N_(CC) ^(DL) PUSCH transmissions with a periodicity of N1subframes, and different cycles have a time-domain offset of N2subframes. An example is given in FIG. 3, which illustrates aperiodictriggering of three cycles of CSI feedback from two DL CCs, where N_(CC)^(DL)=2, M=3.

The second issue is how to signal which DL CC a PUSCH report istargeting. This can be done in a number of ways. A first option is toprovide CQI triggering based on the UL CC that is indicated in thesystem information block Type 2 configuration (SIB2-linkage). This is animplicit mapping scheme wherein the CSI report for one DL CC can only betriggered by UL grant on the same CC, i.e. DL CC=CSICC. Furthermore, theUL grant is transmitted on the SIB2-linked UL CC. For the case ofcross-CC scheduling some modifications are needed for this approach.Exemplary use cases are shown in FIGS. 4A-4C with the SIB2-linkage foreach DL/UL CC pair illustrated.

FIG. 4A illustrates the case where a CQI report for a PCC that isresponsible for SCC 0 can only be triggered by the UL grant conveyed onDL PCC.

FIG. 4B illustrates the case where the UE is configured for cross-CCscheduling. The UE monitors the DL PCC for the PUSCH of the UL PCC andSCC 0. An UL grant for UL PCC triggers a CQI report for the DL PCC. AnUL grant for UL SCC 0 triggers a CQI report for DL SCC 0.

FIG. 4C illustrates the asymmetric CA case where the UE is notconfigured for UL SCC 0, as indicated by the dashed line. To request CQIreport for DL SCC 0, cross-CC scheduling is enabled for SCC1 even thoughit is not configured for the UE. A carrier indication field (CIF) isadded to the UL DCI format for this purpose. In accordance with a RAN2agreement that an UL grant on DL SCC 0 is ignored by the UE, a CQIrequest is sent on DL PCC with a CIF value indicating UL SCC 0. Sincethe UE is not configured to transmit on UL SCC 0 the UE interprets thisDCI as a request for a CQI report from DL SCC 0, and this CQI report issent on the UL PCC.

This is a different way of exploiting the CIF field for aperiodic CQIrequests. An advantage is that it avoids adding a new bit field to DCIformat 0 for aperiodic CQI request. Note that it does not violate theagreement that a UE only monitors the PDCCH on 1 CC for the PUSCH on aconfigured UL CC. It should be clear that this option is not needed forTDD due to symmetric CA.

This scheme produces less impact on UL grant and 1-bit CSI triggeringcan be reused. However, this scheme produces a feedback restriction withunbalanced CSI feedback among CCs. A UE may be configured to monitor ULgrant only in one DL CC semi-statically. Given such a restriction, theCSI report will be limited to a single DL CC semis-statically, and UEwill not be able to feedback CSI for other CCs until the eNBreconfigures the PDCCH monitoring CC.

A second option for signaling which DL CC a PUSCH report is targeting isto perform CSI scanning. This is an implicit mapping scheme wherein oneUL grant triggers consecutive CSI report that scans through all DL CCs,on a periodic basis. A timer needs to be synchronously known at the eNBand UE to understand the CSICC index, e.g. based on the system framenumber (SFN).

A third option for signaling which DL CC a PUSCH report is targeting isto perform explicit mapping. An m-bit CSICC field (m=log 2(N_(CC)^(DL))) may be used to indicate which CSICC that is conveyed on thePUSCH. Alternatively, a fixed 3-bit CSICC field may be used.

A fourth option for signaling which DL CC a PUSCH report is targeting isto perform explicit mapping in which the CSICC field is jointly encodedwith the 1-bit CQI triggering. In this case, m=log 2(N_(CC) ^(DL)+1)bits are needed to jointly indicate the CSI triggering and the CSICCindex.

Options 3 and 4 have the obvious disadvantage of increased UL grantpayload, but only a maximum 3-bits

A fifth option for signaling which DL CC a PUSCH report is targeting isto perform CSI triggering using virtual UL grant. This scheme is aderivative of the implicit triggering approach of Option 1, wherein apositive CSI request is transmitted in a PDCCH on the CC for which anaperiodic CSI report is required. For the asymmetric case shown in FIG.4C, the UE monitors DCI format 0 on DL SCC 0. Although this is not inline with the RAN2 agreement, in any case the UE has to monitor DCIFormat 1A on DL SCC 0. Therefore, there is no savings in number of blinddecodes by not monitoring DCI format 0 since blind decoding is jointlyperformed for both DCI formats 0 and 1A.

In this scheme, a CSI report for DL SCC 0 is transmitted by a virtual ULgrant on DL SCC 0. This UL grant is defined as a virtual UL grant sinceUL SCC 0 is not configured and the UE is not configured for cross-CCscheduling on DL SCC 0. A companion UL grant must be simultaneously senton another DL CC for which the SIB2-linked UL CC is configured for theUE. For example, in FIG. 4C a companion UL grant is sent on the PCC. Ifa positive CSI request is detected on the companion UL grant and thevirtual UL grant, then the UE concatenates aperiodic CSI reports forboth DL CCs on the PUSCH indicated by the companion UL grant. If apositive CSI request is on the virtual UL grant and no CSI request isdetected on the companion UL grant, then the UE transmits aperiodic CSIreport for the DL CC indicated by the virtual UL grant.

Case 2: N_(CC) ^(DL): One UL Grant Triggers CSI Feedback for all N_(CC)^(DL) CCs.

In this case, one PUSCH carries CSI for all DL CCs. The 1-bit CSItriggering in the uplink grant, if enabled, triggers concurrent CSIreport for all DL CCs on the PUSCH. This design has almost no impact onthe UL grant, and the same DCI format can be reused regardless ofcarrier aggregation. On the other hand, a larger CSI payload than Rel-8is present whenever CSI report is triggered. Note that the maximum CSIpayload for one DL CC in Rel-8 is around 100 bits (mode 3-1 withwideband RI/PMI and subband CQI). The DL MIMO double-codebook structurein Rel-10 should not significantly increase the CSI payload (per CC)because the inner codebook (W1) is wideband and incurs marginal CSIoverhead. Hence, assuming the outer codebook (W2) is not significantlylarger than the Rel-8 codebook, the total CSI is approximately 100 bitsfor one CC and 500 bits for five CC. The eNB may simply allocate alarger frequency assignment on PUSCH to accommodate the increased CSIpayload.

Case 3: N ε [1, N_(CC) ^(DL)] is Configurable

The rel-8/9 1-bit CQI request field is extended to a bit map of N_(CC)^(DL) bits wherein a “1” in position x indicates a CQI request for DL CCx and a “0” in position x indicates there is no CQI request for DL CC x.For simplicity, the first bit position (MSB) may represent the PCC whilethe other bit positions may represent the other SCCs in increasingfrequency. However, other bit mappings are not precluded, such as a bitmapping based on the serving cell index.

To avoid ambiguity, during CC activation/deactivation the size of thebit map can be set to the number of configured DL CCs. An illustrationis shown in FIG. 5 for five DL CCs with a CSI feedback for CC1 and CC5using a bitmap.

Allowing a variable set of CCs for aperiodic report has severaladvantages. CSI feedback delay is reduced and CSI accuracy/granularityis improved. Differentiated CSI reporting for different DL CCs isallowed according to the system operation (e.g. buffer status, cellload), where eNB may configure CSI report for each DL CC on a needbasis. For example if the downlink data traffic is low, eNB only needsto schedule UE on a few CCs. In this case the UL grant can trigger CSIfor one or two DLCC that historically has good channel conditionsbecause they are more likely to be used for DL PDSCH transmission. OtherCCs that have poorer CSI history can be omitted in CSI report since theyare less likely used.

CSI payload on PUSCH may be adaptively configured. UE does not need toalways report CSI for all CCs unless it is considered necessary by theeNB.

Such configurability may prove to be beneficial for heterogeneousdeployment scenario. In case one CC experiences high interference fromFemto cell (e.g. due to traffic offloading), the eNB may trigger feweraperiodic CSI reports on the highly interfered CC while requesting morefrequent CSI reports from other CCs.

Similar alternatives, wherein a bitmap is used to configure CSIreporting are not precluded. One alternative is medium access control(MAC) signaling in which the bitmap is configured by MAC signaling. Thismethod solves the issue of the UL grant overhead by (re)configuring thenumber of DL CCs that are indicated by one aperiodic CSI request. Ittrades off the L1 overhead of a CSI request bit map in the UL grant withincreased latency of bit map (re)configuration. The bit map can beplaced in a MAC control element which is conveyed in a PDSCH.

A second alternative for using a bitmap to configure CSI reporting isRRC signaling. This method is the most reliable compared to L1 and L2signaling but it also incurs the most latency in bitmap(re)configuration. The UE is configured by RRC signaling with a bitmapwhich specifies the subset of the configured DL CCs that CSI should bereported for. When the UE detects a positive CSI request in a PDCCH onany of the CSI-CCs in the configured subset, then the UE reports CSI forthe CSI-CCs enabled in the bitmap.

Allowing a variable set of CCs for aperiodic report has some drawbacks.One drawback is increased UL grant overhead that scales linearly withthe number of configured DL carriers. For example, if five DL CCs areconfigured, a 5-bit map is required in the UL grant. However, carrieraggregation of up to five downlink carriers may be a rare case, and asmaller number of carrier aggregation (2-3) represents most of thepredominant use cases. Hence, the differentiated CSI reportingflexibility for different CCs and lower PUSCH overhead appears much morecritical.

The overhead of the bitmap may be reduced by grouping the N_(CC) ^(DL)CCs into subsets with similar properties such as interference condition,such as in heterogeneous network (HetNet) environments. For example, a2-bit CSI triggering field in the UL grant can be used to signal up tothree groupings. One exemplary configuration is as follows:

-   “00” indicates no CSI is triggered-   “01” triggers the SIB2-linked DL CC-   “10” triggers an RRC configured subset of the activated DL CCs-   “11” triggers all activated CCs

Alternatively, “11” can also trigger another RRC-configured subset.

Note that for the case of at most two DL CCs in Rel-10 the 2-bit fieldprovides full flexibility as follows:

-   “00” indicates no CSI is triggered-   “01” triggers the SIB2-linked DL CC-   “10” triggers the other DL CC-   “11” triggers both CCs    UL CC Indication

It is natural for the CSI to be conveyed on the CC which is scheduled bythe UL grant. However, if aperiodic CQI requests are triggered inmultiple UL grants, the UE needs to be signaled which UL CC conveys theCSI, per the 3GPP RAN1 agreement that UCI is transmitted on only onePUSCH. There are two basic options, as follows:

Option 1: reuse the CC priority rules for periodic CSI transmission foraperiodic CSI transmission.

Option 2: if the UE receives multiple UL grants only one UL grant cancontain a positive CSI request.

Option 2 is preferred because it simplifies specification and testingefforts. On the other hand an ambiguous scenario could occur where theUE detects two or more UL grants with positive CSI request. This casecan be viewed as either a faulty eNB implementation or a PDCCH decodingerror by the UE. Since either case should almost never occur, the UEbehavior may be left undefined for this scenario.

Aperiodic CSI Transmission Without UL-SCH Data

Rel-8/9 supports CSI-only transmission on PUSCH by setting the CQIrequest bit to “1”, the modulation and coding set index I_(MCS)=29 andthe number of PRBs in the UL grant N_(PRB)≦4 in DCI format 0. Somemodification is required to support CSI reporting of up to five DL CCson the PUSCH without associated UL-SCH data. At the very least, N_(PRB)must be increased.

One scheme for aperiodic CSI transmission without UL-SCH data for CSIfeedback for N≦N_(CC) ^(DL) CCs is to set CQI request bit to trigger CSIreports for multiple CCs, I_(MCS)=29 and N_(PRB)≦L. To reduce errorcases L should only scale with N_(CC) ^(DL) or with the number ofconfigured DL CCs, i.e. L should not change depending on how many CSIreports are included in particular transmission.

A second scheme is to restrict aperiodic CQI request without UL-SCH datato the Rel-8/9 procedure. This implies that an aperiodic CQI requestfrom multiple DL CCs cannot occur without UL-SCH data. The eNB simplydetermines the appropriate RB allocation to account for the aggregateCSI transmission with an appropriate amount of UL-SCH data. The size ofthe transport block for UL-SCH data is left to eNB implementation.Therefore, for the case where CQI request bit=“1”, I_(MCS)=29 andN_(PRB)≦4, there is only one CSICC, and the UE reports the CQI for theDL CC conveying the UL grant.

FIG. 6 is a flow chart illustrating operation of UE and eNB in thenetwork of FIG. 1 while reporting CSI for aggregated CCs. A UE, such asUE 109, receives 602 two or more reference signals corresponding to twoor more aggregated component carriers (CC) at the user equipment from abase station, such as eNB 101. The aggregated CCs are scheduled by theeNB according to LTE standards. Reference signals are transmitted by theeNB to the UE as described in more detail above.

The UE computes 604 a set of channel state information (CSI) estimatesderived from the two or more reference signals corresponding to the twoor more CCs. The CSI is computed using known techniques according to LTEstandards.

The UE receives 606 a positive CSI request from the eNB for a CSI reportand in response transmits 608 CSI feedback from the UE to the eNBcomprising one or more CSI reports selected from the plurality of CSIestimates.

The UE may also receive 606 with the CSI request a bit map from the eNBthat specifies a subset of the two or more CCs. The bit map may beexplicit, or it may be encoded. The CSI that is transmitted 608 to thebase station contains CSI reports for the CCs specified by the bit map.

The UE may receive 606 a plurality of uplink grants from the eNB for thetwo or more aggregated component carriers. The positive CSI request iscontained within only one of the plurality of uplink grants from theeNB.

System Example

FIG. 7 is a block diagram illustrating an exemplary portion of thecellular network of FIG. 1. As shown in FIG. 7, the wireless networkingsystem 1000 includes a UE device 1001 in communication with an eNB 1002.The UE device 1001 may represent any of a variety of devices such as aserver, a desktop computer, a laptop computer, a cellular phone, aPersonal Digital Assistant (PDA), a smart phone or other electronicdevices. In some embodiments, the electronic UE device 1001 communicateswith the eNB 1002 based on a LTE or E-UTRA protocol. Alternatively,another communication protocol now known or later developed may be used.

As shown, UE device 1001 includes a processor 1003 coupled to a memory1007 and a Transceiver 1004. The memory 1007 stores (software)applications 1005 for execution by the processor 1003. The applications1005 could be any known or future application useful for individuals ororganizations. As an example, such applications 1005 could becategorized as operating systems (OS), device drivers, databases,multimedia tools, presentation tools, Internet browsers, e-mailers,Voice-Over-Internet Protocol (VOIP) tools, file browsers, firewalls,instant messaging, finance tools, games, word processors or othercategories. Regardless of the exact nature of the applications 1005, atleast some of the applications 1005 may direct eNB (base-station) 1002to transmit DL signals to UE device 1001 periodically or continuouslyvia the transceiver 1004.

Transceiver 1004 includes uplink logic which may be implemented byexecution of instructions that control the operation of the transceiver.Some of these instructions may be stored in memory 1007 and executedwhen needed. As would be understood by one of skill in the art, thecomponents of the uplink and downlink logic may involve the physical(PHY) layer and/or the Media Access Control (MAC) layer of thetransceiver 1004. Transceiver 1004 includes two or more receivers 1020and two or more transmitters 1022 for SU/MU-MIMO, as described in moredetail above.

eNB 1002 includes a Processor 1009 coupled to a memory 1013 and atransceiver 1010. Memory 1013 stores applications 1008 for execution bythe processor 1009. The applications 1008 could be any known or futureapplication useful for managing wireless communications. At least someof the applications 1008 may direct the base-station to managetransmissions to or from the user device 1001.

Transceiver 1010 includes a resource manager which enables eNB 1002 toselectively allocate uplink PUSCH resources and downlink PDSCH resourcesto the user device 1001. As would be understood by one of skill in theart, the components of the resource manager 1012 may involve thephysical (PHY) layer and/or the Media Access Control (MAC) layer of thetransceiver 1010. Transceiver 1010 includes a Receiver 1011 forreceiving transmissions from various UE within range of the eNB andtransmitter 1014 for transmission to the various UE within range. Theresource manager executes instructions that control the operation oftransceiver 1010. Some of these instructions may be located in memory1013 and executed when needed. The resource manager controls thetransmission resources allocated to each UE that is being served by eNB1002 and broadcasts control information via the physical downlinkcontrol channel PDCCH.

During MIMO transmission from eNB 1002 via transmitters 1014 on PDSCH,eNB 1002 monitors channel conditions to adapt to the prevailingcondition. This includes monitoring the channel quality indicator (CQI)and precoding matrix index (PMI) feedback provided by UE 1001 on theuplink channel using condition monitoring logic 1012 that is coupled toreceiver 1011. As was described in more detail above, the enhancedCQI/PMI feedback includes periodic and aperiodic CSI reports foraggregated CCs.

During MIMO transmission to UE 1001 via transmitters 1014 on PDSCH, eNB1002 forms DMRS signals, depending on the number of layers being usedfor transmission, as described in more detail above.

A typical eNB will have multiple sets of receivers and transmitterswhich operate generally as described herein to support hundreds orthousand of UE within a given cell. Each transmitter may be embodiedgenerally by a processor 1009 that executes instructions from memory1013 to perform the scrambling, mapping, and OFDM signal formation,using signal processing techniques as are generally known in the artalong with embodiments of the invention described herein.

As described in more detail above, the eNB transmits a reference signalfor reception by a UE. The eNB then receives feedback from the UEcomprising periodic and aperiodic CSI reports for aggregated CCs thathave been scheduled by the eNB for the UE. The eNB uses the CQI for eachof the two or more ranks and the PMI included in the feedback to selecta precoding matrix for use by the eNB for transmission of data to the UEin single user or in multiuser transmission modes.

Other Embodiments

While the invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various other embodiments of the invention will beapparent to persons skilled in the art upon reference to thisdescription. For example, a larger or smaller number of symbols thendescribed herein may be used in a slot.

While the invention has been described with reference to DLtransmission, it may be equally applied to UL transmission.

Embodiments of the invention may support single user (SU) dual-layerbeamforming in LTE Rel-10 for both LTE-TDD (time division duplex) andFDD (frequency division duplex) using UE specific demodulation referencesignals and mapping of physical data channel to resource elements.Embodiments of the invention are also applicable to spatial multiplexing(MIMO) of up to eight layers in LTE Rel-10, and may be extended tospatial multiplexing with more than eight layers in future advancedcommunication systems.

The term “frame” and “subframe” are not restricted to the structure ofFIG. 2. Other configurations of frames and/or subframes may be embodied.In general, the term “frame” may refer to a set of one or moresubframes. A transmission instance likewise refers to a frame, subframe,or other agreed upon quantity of transmission resource.

Embodiments of this invention apply to various types of frequencydivision multiplex based transmission. Thus, the concept can easily beapplied to: OFDMA, OFDM, DFT-spread OFDM, DFT-spread OFDMA, SC-OFDM,SC-OFDMA, MC-CDMA, and all other FDM—based transmission strategies.

A NodeB is generally a fixed station and may also be called a basetransceiver system (BTS), an access point, or some other terminology. AUE, also commonly referred to as terminal or mobile station, may befixed or mobile and may be a wireless device, a cellular phone, apersonal digital assistant (PDA), a wireless modem card, and so on.

As described in general above, an embodiment of the invention mayperform all tasks described herein such as channel monitoring andprecoding selection, formation of transmission signals, etc, using logicimplemented by instructions executed on a processor. Another embodimentmay have particular hardwired circuitry or other special purpose logicoptimized for performing one or more to the tasks described herein.

An embodiment of the invention may include a system with a processorcoupled to a computer readable medium in which a software program isstored that contains instructions that when executed by the processorperform the functions of modules and circuits described herein. Thecomputer readable medium may be memory storage such as dynamic randomaccess memory (DRAM), static RAM (SRAM), read only memory (ROM),Programmable ROM (PROM), erasable PROM (EPROM) or other similar types ofmemory. The computer readable media may also be in the form of magnetic,optical, semiconductor or other types of discs or other portable memorydevices that can be used to distribute the software for downloading to asystem for execution by a processor. The computer readable media mayalso be in the form of magnetic, optical, semiconductor or other typesof disc unit coupled to a system that can store the software fordownloading or for direct execution by a processor.

As used herein, the terms “applied,” “coupled,” “connected,” and“connection” mean electrically connected, including where additionalelements may be in the electrical connection path. “Associated” means acontrolling relationship, such as a memory resource that is controlledby an associated port.

It is therefore contemplated that the appended claims will cover anysuch modifications of the embodiments as fall within the true scope andspirit of the invention.

What is claimed is:
 1. A method of operating a user equipment device ina cellular network, the method comprising: receiving two or morereference signals corresponding to two or more aggregated componentcarriers (CC); receiving a positive channel state information (CSI)request that specifies one of at least two subsets of the two or moreaggregated CCs; computing a plurality of CSI estimates derived from thetwo or more reference signals for the specified subset of the two ormore aggregated CCs; and transmitting CSI feedback comprising one ormore CSI reports based upon the plurality of CSI estimates for thespecified subset wherein the CSI feedback includes either a precodingmatrix indicator (PMI) or a rank indication (RI).
 2. The method of claim1, wherein the CSI request is a 2-bit field in which one or more valuesindicate different subsets of the two or more aggregated CCs.
 3. Themethod of claim 2, wherein said subsets are semi-statically configuredby RRC signaling.
 4. A method of operating a user equipment device in acellular network, the method comprising: receiving two or more referencesignals corresponding to two or more aggregated component carriers (CC);receiving a plurality of uplink grants for the two or more aggregatedcomponent carriers, wherein a positive channel state information (CSI)request is contained within only one of the plurality of uplink grants;computing at least one CSI estimate derived from the two or morereference signals for each of the two or more aggregated CCs; andtransmitting CSI feedback on the CC indicated by the uplink grantcontaining the positive CSI request comprising one or more CSI reportsselected from the at least one CSI estimate wherein the CSI feedbackincludes either a precoding matrix indicator (PMI) or a rank indication(RI).
 5. A method of operating a user equipment device in a cellularnetwork, the method comprising: receiving two or more reference signalscorresponding to two or more aggregated component carriers (CC);computing a plurality of channel state information (CSI) estimatesderived from the two or more reference signals for each of the two ormore aggregated CCs; receiving a positive CSI request for one or moreCSI reports; and transmitting CSI feedback comprising the one or moreCSI reports specified by the CSI request, wherein there is no associateduplink shared (UL-SCH) data on a physical uplink shared channel (PUSCH)indicated by a modulation and coding scheme index value equal to 29 anda resource allocation of a number of physical resource blocks no greaterthan a fixed number that does not vary with the number of configuredCCs.
 6. A method of operating a base station in a cellular network, themethod comprising: transmitting two or more reference signalscorresponding to two or more aggregated component carriers (CC);transmitting a positive channel state information (CSI) request thatspecifies one of at least two subsets of the two or more aggregated CCs;and receiving CSI feedback comprising one or more CSI reports for thesubset specified by the CSI request wherein the CSI feedback includeseither a precoding matrix indicator (PMI) or a rank indication (RI). 7.The method of claim 6, wherein the CSI request is a 2-bit field in whichone or more values indicate different subsets of the two or moreaggregated CCs.
 8. The method of claim 7, wherein said subsets aresemi-statically configured by RRC signaling.
 9. A method of operating abase station in a cellular network, the method comprising: transmittingtwo or more reference signals corresponding to two or more aggregatedcomponent carriers (CC); transmitting a plurality of uplink grants forthe two or more aggregated component carriers, wherein a positivechannel state information (CSI) request is contained within only one ofthe plurality of uplink grants; and receiving CSI feedback comprisingone or more CSI reports selected according to the positive CSI requestwherein the CSI feedback includes either a precoding matrix indicator(PMI) or a rank indication (RI).
 10. A method of operating a basestation in a cellular network, the method comprising: transmitting twoor more reference signals corresponding to two or more aggregatedcomponent carriers (CC); transmitting a positive channel stateinformation (CSI) request for the one or more CSI reports from aplurality of CSI estimates derived from the two or more referencesignals for each of the two or more aggregated CCs; and receiving theCSI feedback comprising the one or more CSI reports specified by the CSIrequest, wherein there is no associated (UL-SCH) data on a physicaluplink shared channel (PUSCH) indicated by a modulation and codingscheme index value equal to 29 and a resource allocation of a number ofphysical resource blocks no greater than a fixed number that does notvary with the number of configured CCs.
 11. A user equipment device foruse in a cellular network, the device comprising: circuitry forreceiving two or more reference signals corresponding to two or moreaggregated component carriers (CC); circuitry for receiving a CSIrequest that specifies one of at least two subsets of the two or moreaggregated CCs; and circuitry for transmitting channel state information(CSI) feedback comprising one or more CSI reports for the subsetspecified by the CSI request wherein the CSI feedback includes either aprecoding matrix indicator (PMI) or a rank indication (RI).
 12. Thedevice of claim 11, wherein the CSI request is a 2-bit field in whichone or more values indicate different subsets of the two or moreaggregated CCs.
 13. The device of claim 12, wherein said subsets aresemi-statically configured by RRC signaling.
 14. The device of claim 11,further comprising a processor coupled to the circuitry for transmittingand to the circuitry for receiving two or more reference signals, theprocessor configured to compute a plurality of CSI estimates derivedfrom the two or more reference signals for the subset of the two or moreaggregated CCs.
 15. The device of claim 14, wherein the processor isfurther configured to receive a plurality of uplink grants for the twoor more aggregated component carriers, wherein a positive CSI request iscontained within only one of a plurality of uplink grants.
 16. A methodof operating a user equipment device in a cellular network, the methodcomprising: receiving two or more reference signals corresponding to twoor more aggregated component carriers (CC); receiving a channel stateinformation (CSI) request that specifies one of at least two subsets ofthe two or more aggregated CCs; and computing at least one precodingmatrix indicator (PMI) or rank indication (RI) derived from the two ormore reference signals for the subset.
 17. The method of claim 16,wherein the CSI request is a 2-bit field in which one or more valuesindicate different subsets of the two or more aggregated CCs.
 18. Amethod of operating a user equipment device in a cellular network, themethod comprising: receiving two or more reference signals correspondingto two or more aggregated component carriers (CC); receiving a pluralityof uplink grants for the two or more aggregated component carriers,wherein a positive channel state information (CSI) request is containedwithin only one of the plurality of uplink grants; and computing atleast one precoding matrix indicator (PMI) or rank indication (RI)derived from the two or more reference signals for each of the two ormore aggregated CCs.
 19. A user equipment device for use in a cellularnetwork, the device comprising: circuitry for receiving two or morereference signals corresponding to two or more aggregated componentcarriers (CC); circuitry for receiving a CSI request that specifies oneof at least two subsets of the two or more aggregated CCs, wherein thesubsets are Radio Resource Control (RRC) configured; and circuitry forcomputing at least one precoding matrix indicator (PMI) or rankindication (RI) derived from the two or more reference signals for thesubset.
 20. The device of claim 19, wherein the CSI request is a 2-bitfield in which one or more values indicate different subsets of the twoor more aggregated CCs.
 21. A method of operating a user equipmentdevice in a cellular network, the method comprising: receiving two ormore reference signals corresponding to two or more aggregated componentcarriers (CC); receiving a positive CSI request for a subset of two ormore aggregated CCs; computing a plurality of channel state information(CSI) estimates derived from the two or more reference signals for theCSI request; and transmitting CSI feedback comprising two or more CSIreports selected from the plurality of CSI estimates, wherein there isno associated uplink shared (UL-SCH) data on a physical uplink sharedchannel (PUSCH) indicated by a modulation and coding scheme index valueequal to 29 and a resource allocation of a number of physical resourceblocks no greater than a fixed number that does not vary with the numberof configured CCs.
 22. A method of operating a base station in acellular network, the method comprising: transmitting two or morereference signals corresponding to two or more aggregated componentcarriers (CC); transmitting a positive channel state information (CSI)request for a subset of the two or more CCs from a plurality of CSIestimates derived from the two or more reference signals for the subsetof the two or more aggregated CCs; and receiving CSI feedback comprisingtwo or more CSI reports for the subset of the two or more aggregatedCCs, wherein there is no associated (UL-SCH) data on a physical uplinkshared channel (PUSCH) indicated by a modulation and coding scheme indexvalue equal to 29 and a resource allocation of a number of physicalresource blocks no greater than a fixed number that does not vary withthe number of configured CCs.
 23. A user equipment device for use in acellular network, the device comprising: circuitry for receiving two ormore reference signals corresponding to two or more aggregated componentcarriers (CC); circuitry for transmitting channel state information(CSI) feedback comprising one or more CSI reports selected from aplurality of CSI estimates in response to a positive CSI requestreceived for the one or more CSI reports; a processor coupled to thecircuitry for transmitting and to the circuitry for receiving, theprocessor configured to compute the plurality of CSI estimates derivedfrom the two or more reference signals for each of the two or moreaggregated CCs, wherein the processor is further configured to: receivea CSI request from the eNB that specifies a subset of the two or moreaggregated CCs; and select CSI estimates for the subset specified by theCSI request for transmission of the CSI feedback; and wherein there isno associated uplink shared (UL-SCH) data on a physical uplink sharedchannel (PUSCH) indicated by a modulation and coding scheme index valueequal to 29 and a resource allocation of a number of physical resourceblocks no greater than a fixed number that does not vary with the numberof configured CCs.